Update README with new benchmark

Closes #27

Bench.cpp

@@ -258,4 +258,75 @@ void benchConflictSet() {
   }
 }
 
-int main(void) { benchConflictSet(); }
+void benchWorstCaseForRadixRangeRead() {
+  ankerl::nanobench::Bench bench;
+  ConflictSet cs{0};
+
+  int64_t version = 0;
+
+  constexpr int kKeyLength = 50;
+
+  for (int i = 0; i < kKeyLength; ++i) {
+    for (int j = 0; j < 256; ++j) {
+      auto b = std::vector<uint8_t>(i, 0);
+      b.push_back(j);
+      auto e = std::vector<uint8_t>(i, 255);
+      e.push_back(j);
+      weaselab::ConflictSet::WriteRange w[] = {{
+                                                   {b.data(), int(b.size())},
+                                                   {nullptr, 0},
+                                               },
+                                               {
+                                                   {e.data(), int(e.size())},
+                                                   {nullptr, 0},
+                                               }};
+      cs.addWrites(w, sizeof(w) / sizeof(w[0]), version);
+    }
+  }
+
+  // Defeat short-circuiting on the left
+  {
+    auto k = std::vector<uint8_t>(kKeyLength, 0);
+    weaselab::ConflictSet::WriteRange w[] = {
+        {
+            {k.data(), int(k.size())},
+            {nullptr, 0},
+        },
+    };
+    cs.addWrites(w, sizeof(w) / sizeof(w[0]), 2);
+  }
+
+  // Defeat short-circuiting on the right
+  {
+    auto k = std::vector<uint8_t>(kKeyLength, 255);
+    weaselab::ConflictSet::WriteRange w[] = {
+        {
+            {k.data(), int(k.size())},
+            {nullptr, 0},
+        },
+    };
+    cs.addWrites(w, sizeof(w) / sizeof(w[0]), 2);
+  }
+
+  auto begin = std::vector<uint8_t>(kKeyLength - 1, 0);
+  begin.push_back(1);
+  auto end = std::vector<uint8_t>(kKeyLength - 1, 255);
+  end.push_back(254);
+
+  weaselab::ConflictSet::Result result;
+  weaselab::ConflictSet::ReadRange r{
+      {begin.data(), int(begin.size())}, {end.data(), int(end.size())}, 1};
+
+  bench.run("worst case for radix tree", [&]() {
+    result = weaselab::ConflictSet::TooOld;
+    cs.check(&r, &result, 1);
+    if (result != weaselab::ConflictSet::Commit) {
+      abort();
+    }
+  });
+}
+
+int main(void) {
+  benchConflictSet();
+  benchWorstCaseForRadixRangeRead();
+}

ConflictSet.cpp

@@ -1621,28 +1621,31 @@ downLeftSpine:
   }
 }
 
-// Return the max version among all keys starting with the search path of n +
-// [child], where child in (begin, end). Does not account for the range version
-// of firstGt(searchpath(n) + [end - 1])
-int64_t maxBetweenExclusive(Node *n, int begin, int end) {
+// Return whether or not the max version among all keys starting with the search
+// path of n + [child], where child in (begin, end) is <= readVersion. Does not
+// account for the range version of firstGt(searchpath(n) + [end - 1])
+bool checkMaxBetweenExclusive(Node *n, int begin, int end,
+                              int64_t readVersion) {
   assume(-1 <= begin);
   assume(begin <= 256);
   assume(-1 <= end);
   assume(end <= 256);
   assume(begin < end);
-  int64_t result = std::numeric_limits<int64_t>::lowest();
   {
     int c = getChildGeq(n, begin + 1);
     if (c >= 0 && c < end) {
       auto *child = getChildExists(n, c);
       if (child->entryPresent) {
-        result = std::max(result, child->entry.rangeVersion);
+        if (!(child->entry.rangeVersion <= readVersion)) {
+          return false;
+        };
       }
       begin = c;
     } else {
-      return result;
+      return true;
     }
   }
+
   switch (n->getType()) {
   case Type_Node0: // GCOVR_EXCL_LINE
     // We would have returned above, after not finding a child
@@ -1651,7 +1654,9 @@ int64_t maxBetweenExclusive(Node *n, int begin, int end) {
     auto *self = static_cast<Node3 *>(n);
     for (int i = 0; i < self->numChildren && self->index[i] < end; ++i) {
       if (begin <= self->index[i]) {
-        result = std::max(result, self->children[i].childMaxVersion);
+        if (self->children[i].childMaxVersion > readVersion) {
+          return false;
+        }
       }
     }
   } break;
@@ -1659,37 +1664,45 @@ int64_t maxBetweenExclusive(Node *n, int begin, int end) {
     auto *self = static_cast<Node16 *>(n);
     for (int i = 0; i < self->numChildren && self->index[i] < end; ++i) {
       if (begin <= self->index[i]) {
-        result = std::max(result, self->children[i].childMaxVersion);
+        if (self->children[i].childMaxVersion > readVersion) {
+          return false;
+        }
       }
     }
   } break;
   case Type_Node48: {
+    bool conflict[256] = {};
     auto *self = static_cast<Node48 *>(n);
     self->bitSet.forEachInRange(
         [&](int i) {
-          result =
-              std::max(result, self->children[self->index[i]].childMaxVersion);
+          conflict[i] =
+              self->children[self->index[i]].childMaxVersion > readVersion;
         },
         begin, end);
-    break;
+    bool result = true;
+    for (auto c : conflict) {
+      result &= !c;
+    }
+    return result;
   }
   case Type_Node256: {
+    bool conflict[256] = {};
     auto *self = static_cast<Node256 *>(n);
     self->bitSet.forEachInRange(
         [&](int i) {
-          result = std::max(result, self->children[i].childMaxVersion);
+          conflict[i] = self->children[i].childMaxVersion > readVersion;
         },
         begin, end);
-    break;
+    bool result = true;
+    for (auto c : conflict) {
+      result &= !c;
+    }
+    return result;
   }
   default:                   // GCOVR_EXCL_LINE
     __builtin_unreachable(); // GCOVR_EXCL_LINE
   }
-#if DEBUG_VERBOSE && !defined(NDEBUG)
-  fprintf(stderr, "At `%s', max version in (%02x, %02x) is %" PRId64 "\n",
-          getSearchPathPrintable(n).c_str(), begin, end, result);
-#endif
-  return result;
+  return true;
 }
 
 Vector<uint8_t> getSearchPath(Arena &arena, Node *n) {
@@ -1722,7 +1735,7 @@ bool checkRangeStartsWith(Node *n, std::span<const uint8_t> key, int begin,
 #endif
   auto remaining = key;
   if (remaining.size() == 0) {
-    return maxBetweenExclusive(n, begin, end) <= readVersion;
+    return checkMaxBetweenExclusive(n, begin, end, readVersion);
   }
 
   auto *child = getChild(n, remaining[0]);
@@ -1821,7 +1834,7 @@ struct CheckRangeLeftSide {
       }
 
       if (searchPathLen >= prefixLen) {
-        if (maxBetweenExclusive(n, remaining[0], 256) > readVersion) {
+        if (!checkMaxBetweenExclusive(n, remaining[0], 256, readVersion)) {
           ok = false;
           return true;
         }
@@ -1963,7 +1976,7 @@ struct CheckRangeRightSide {
           return true;
         }
 
-        if (maxBetweenExclusive(n, -1, remaining[0]) > readVersion) {
+        if (!checkMaxBetweenExclusive(n, -1, remaining[0], readVersion)) {
           ok = false;
           return true;
         }

README.md

@@ -58,27 +58,29 @@ Performance counters:
 
 ## Skip list
 
-|  ns/op |         op/s | err% | total | benchmark                           |
-| -----: | -----------: | ---: | ----: | :---------------------------------- |
-| 246.99 | 4,048,700.59 | 0.2% |  0.01 | `point reads`                       |
-| 260.16 | 3,843,784.65 | 0.1% |  0.01 | `prefix reads`                      |
-| 493.35 | 2,026,953.19 | 0.1% |  0.01 | `range reads`                       |
-| 462.05 | 2,164,289.23 | 0.6% |  0.01 | `point writes`                      |
-| 448.19 | 2,231,205.25 | 0.9% |  0.01 | `prefix writes`                     |
-| 255.83 | 3,908,845.72 | 1.5% |  0.02 | `range writes`                      |
-| 582.63 | 1,716,349.02 | 1.3% |  0.01 | `monotonic increasing point writes` |
+|               ns/op |                op/s |    err% |     total | benchmark
+|--------------------:|--------------------:|--------:|----------:|:----------
+|              255.20 |        3,918,570.44 |    0.1% |      0.01 | `point reads`
+|              269.35 |        3,712,633.44 |    0.8% |      0.01 | `prefix reads`
+|              502.72 |        1,989,186.40 |    0.4% |      0.01 | `range reads`
+|              456.85 |        2,188,902.27 |    0.6% |      0.01 | `point writes`
+|              444.81 |        2,248,148.60 |    0.7% |      0.01 | `prefix writes`
+|              250.00 |        4,000,000.00 |    1.7% |      0.02 | `range writes`
+|              566.51 |        1,765,186.07 |    0.5% |      0.01 | `monotonic increasing point writes`
+|              226.41 |        4,416,703.74 |    0.5% |      0.01 | `worst case for radix tree`
 
 ## Radix tree (this implementation)
 
-|  ns/op |          op/s | err% | total | benchmark                           |
-| -----: | ------------: | ---: | ----: | :---------------------------------- |
-|  19.42 | 51,483,206.67 | 0.3% |  0.01 | `point reads`                       |
-|  58.43 | 17,115,612.57 | 0.1% |  0.01 | `prefix reads`                      |
-| 216.09 |  4,627,766.60 | 0.2% |  0.01 | `range reads`                       |
-|  28.35 | 35,267,567.72 | 0.2% |  0.01 | `point writes`                      |
-|  43.43 | 23,026,226.17 | 0.2% |  0.01 | `prefix writes`                     |
-|  50.00 | 20,000,000.00 | 0.0% |  0.01 | `range writes`                      |
-|  92.38 | 10,824,863.69 | 4.1% |  0.01 | `monotonic increasing point writes` |
+|               ns/op |                op/s |    err% |     total | benchmark
+|--------------------:|--------------------:|--------:|----------:|:----------
+|               19.60 |       51,025,020.51 |    0.1% |      0.01 | `point reads`
+|               55.62 |       17,980,734.93 |    0.7% |      0.01 | `prefix reads`
+|              174.86 |        5,718,896.02 |    0.4% |      0.01 | `range reads`
+|               28.27 |       35,372,166.39 |    0.1% |      0.01 | `point writes`
+|               43.85 |       22,804,171.49 |    0.5% |      0.01 | `prefix writes`
+|               49.59 |       20,165,355.92 |    0.9% |      0.01 | `range writes`
+|               92.04 |       10,864,732.33 |    3.6% |      0.01 | `monotonic increasing point writes`
+|            6,937.00 |          144,154.53 |    0.2% |      0.01 | `worst case for radix tree`
 
 # "Real data" test
 

apple-symbol-imports.txt

@@ -1,3 +1,5 @@
+___stack_chk_fail
+___stack_chk_guard
 __tlv_bootstrap
 _abort
 _bzero